1. Field of the Invention
The present invention relates to a method and apparatus for dehydrating matter and, more particularly, to such a method and apparatus which are particularly well suited to the preservation of vegetive matter, such as fruit, in a dehydrated form which is of superior commercial quality and without the use of hazardous substances heretofore required by the prior art.
2. Description of the Prior Art
Preservation of food stuffs is one of the earliest technologic; developed by the human race. Without the capability of preserving perishable commodities in some form, human life cannot be sustained. As a consequence, the technologies developed through the centuries directed to this purpose are highly developed and diverse.
Nonetheless, since the products resulting from the practice of these technologies are ingested, sensitivity to potentially toxic substances borne by such food products is of continual concern. While experience through the ages has developed well entrenched principals as to which technologies may not be tolerated, a more recent public sensitivity to long range potential residual injury has indicated that some traditional technologies may nonetheless be objectionable.
For example, various processes have been developed for preserving vegetive matter and particularly fruit by dehydration producing such dried fruits as peaches, apricots, and grapes thereby forming raisins. More specifically, for example, apricots and golden seedless raisins are produced by pretreatment of the fresh fruit by dipping in a solution of water and sodium hydroxide heated to a temperature of 180.degree. Fahrenheit for 5 to 10 seconds. The fruit is subsequently exposed to a high concentration of sulfur dioxide applied in a gaseous form or, more traditionally, as a product of the combustion of elemental sulfur for this purpose. In the case of golden seedless raisins, the exposure of the fruit to sulfur dioxide bleaches the fruit to a bright yellow and commercially acceptable color thereby reversing the discoloration of the fruit which results from the heat of the pretreatment and dehydration. Residual sulfur dioxide adheres to the fruit tissue inhibiting discoloration due to oxidation and preserving the golden color of the fruit for as long as one year.
While the beneficial effects of the residual sulfur dioxide in inhibiting discoloration and preserving of the fruit for a lengthy period of time has long been recognized, more recently the potentially detrimental effects of its presence have been identified. The presence of sulfur on the fruit tissue in any of its several forms, has been identified by certain scientific authorities as harmful, or potentially harmful, when ingested.
A secondary consequence of such identification is the fact that governmental organizations, particularly in Europe, have banned the import of food stuffs retaining any residual sulfur. Since the state of technology in the production of commercially acceptable golden seedless raisins, for example, is solely dependent upon the use of sulfur in any of its various forms, these governmental bans have indirectly eliminated the market for such products in these countries.
The foregoing example is representative of a number of technologies directed to the preservation of food stuffs which have become inadequate due to the sensitivity of scientific and governmental authorities to the presence of residual substances adhering to the food stuffs as a result of the technology employed in its preservation. The attendant closing of these markets domestically and in foreign countries has in many instances dealt crippling blows to the agricultural industries devoted thereto.
Therefore, it has long been known that it would be desirable to have a method and apparatus for dehydrating matter having application to a wide variety of types of food stuffs which operate rapidly and dependably to preserve the matter in a state which is of superior commercial value while operating only with the use of benign substances and techniques which leave substantially no residual harmful substances on the food stuffs, but which in all other respects produce an entirely commercially successful product.